Apple macOS, iOS, watchOS Kernel Type Confusion Vulnerability Analysis and Mitigation Guide (CVE-2020-27932)

1. Vulnerability Overview & Root Cause

This vulnerability (CVE-2020-27932) is a critical type confusion (CWE-843) flaw residing in the 'Turnstiles' synchronization mechanism of the Apple XNU kernel. Turnstiles are internal kernel structures designed to prevent priority inversion by tracking relationships between threads and synchronization primitives. The root cause lies in inadequate state handling and insufficient type validation when the kernel processes these synchronization objects, allowing an object of one type to be mistakenly treated as another.

2. Exploitation Mechanics & Attack Scenario

An attacker initiates the exploit by running a malicious, unprivileged application on the target device (often bypassing initial sandbox restrictions). The application invokes specific system calls designed to manipulate Turnstile allocations. Due to the state handling flaw, the kernel misinterprets a user-controlled object or port as a Turnstile structure. This type confusion allows the attacker to corrupt kernel memory, overwrite critical function pointers, and hijack the control flow, leading to Local Privilege Escalation (LPE) and arbitrary code execution in the kernel context.

3. Infrastructure & Business Impact

As a vulnerability listed in the CISA KEV catalog, this flaw has been actively exploited in the wild. Successful exploitation grants the attacker complete control over the compromised endpoint (Mac, iPhone, or Apple Watch). In an enterprise environment, this can lead to the compromise of high-value developer or executive workstations, enabling lateral movement within the corporate network, credential theft from the system keychain, and unauthorized access to sensitive intellectual property.